【Blockade】 , 【siege】 are comparable when denoting an attempt of a belligerent force to break down the resistance of the enemy by preventing egress or ingress of men or entrance of supplies over a considerable period of time.
【Blockade】 is used chiefly of an attempt made to close a port, harbor, or coast, especially by effectively investing it with warships or with mines so that fresh supplies (as of food, fuel, and ammunition) are cut off from the enemy.
【Siege】 is applied chiefly to a military as opposed to a naval attempt. The term implies investment with troops on all sides of a fortified place (often a city).
It also suggests, as 【blockade】 does not, frequent assaults by the besieging forces as efforts to compel surrender.
